Teeth brush very carefully but still got tooth decay, why?

The bacteria ferment carbohydrates during acid nutrition of beings. Acid solubility of tooth enamel minerals. Long day on the teeth caused deep.

Defects of tooth enamel, there are 2 main reasons:

The enamel in acid soluble components by structure depending minerals in the enamel surface

Enamel surface more hollow, but it's hard to close food wash brush. Food is a source of nutrition of bacteria, acid causes cavities in the grooves eggs.

Therefore, only brushing your teeth is not enough to keep teeth from decay